How can I use outputcache at this situation?

Question

In my application, I will remember user's language choice in session. The problem is if I use output cache, then the change language function will not work, because it caches the result when I retrieve from database according to the Session["lang"] value.

So if I have another method to use cache function ? Or how can I decrease the response time ?

Answer 1

Part of the Output Caching infrastructure is the VaryBy mechanism, which is a way to instruct ASP.NET to keep parallel caches of the same page varied by some piece of data, like a querystring. In this case, the VaryByCustom mechanism may be the simplest to implement. Here's a short article with a good example.

First, the caching attribute:

[OutputCache(CacheProfile = "CachedPage")]
public ActionResult Index()
{
   return View();
}

The cache profile:

<caching>
    <outputcachesettings>             
        <outputcacheprofiles> 
            <add varybycustom="Language"
                 varybyparam="*"
                 duration="86400"
                 name="CachedPage" />
        </outputcacheprofiles> 
    </outputcachesettings> 
</caching>

And finally, the custom logic in global.asax.cs:

public override string GetVaryByCustomString(
    HttpContext context,
    string arg)
{
    if (arg == "Language")
    {
         return Session["lang"].ToString();
    }
    else
    {
        return base.GetVaryByCustomString(context, arg);
    }
}

Now for each possible unique value that Session["lang"] returns, ASP.NET will keep a cached copy of the page which executed under that parameter.